Knee cartilage does not regrow on its own in any meaningful way. The smooth, glassy cartilage lining your knee joint has almost no blood supply, which means your body can’t deliver the repair cells and nutrients it sends to heal other tissues like skin or bone. Once that cartilage is damaged or worn away, the loss is essentially permanent without medical intervention. The good news: several surgical procedures can restore cartilage in the right candidates, and practical steps like weight loss can dramatically reduce further damage.
Why Cartilage Can’t Heal Itself
Most tissues in your body repair themselves through a predictable cycle: blood rushes to the injury, delivers immune cells and growth factors, and new tissue forms. Cartilage never gets that process started because it has no blood vessels running through it. Instead, cartilage cells get their oxygen and nutrients passively, through slow diffusion from the surrounding joint fluid and underlying bone. That trickle is enough to keep healthy cartilage alive, but nowhere near enough to fuel a repair response.
The cells inside cartilage (chondrocytes) also work against recovery. In adults, these cells have very low activity. They divide slowly and produce minimal new structural material. The collagen fibers that give cartilage its strength are essentially the same ones you’ve had since you stopped growing, with almost no turnover.
When your body does attempt a repair after cartilage damage, it typically produces fibrocartilage, a rougher, weaker tissue that doesn’t hold up like the original. Fibrocartilage lacks the smooth, low-friction surface of healthy (hyaline) cartilage and tends to break down faster under the loads your knee handles every day. This is the central challenge in every cartilage treatment: getting the body to produce real hyaline cartilage rather than this inferior substitute.
How Doctors Grade Cartilage Damage
The severity of cartilage loss is graded on a 0-to-4 scale. Grade 0 is normal, healthy cartilage. Grades 1 and 2 represent relatively minor damage: softening, shallow fissures, or defects that extend less than halfway through the cartilage’s depth. Grade 3 means the defect goes more than halfway down, reaching close to the bone underneath. Grade 4 is a full-thickness loss where the cartilage is completely gone and the underlying bone is exposed.
This grading matters because it determines which treatments are realistic. Mild damage (grades 1-2) can often be managed without surgery. Grades 3 and 4 are where surgical cartilage restoration becomes relevant, though not every patient with severe damage is a good candidate.
Surgical Options That Restore Cartilage
Several procedures exist that can fill cartilage defects with new tissue. Each works best for a specific type of damage, and all share a common limitation: they work best in younger, active adults with a single area of damage rather than widespread joint deterioration.
Microfracture
This is the simplest approach. A surgeon pokes tiny holes into the bone beneath the damaged area, which causes bleeding into the defect. The blood brings stem cells that form a clot, which eventually matures into a repair tissue. The catch is that the tissue produced is mostly fibrocartilage, not the durable hyaline cartilage you started with. Long-term results reflect this: at 10 years, only about 46% of athletes who had microfracture could return to their previous level of sport, and 38% needed a revision procedure. Microfracture works best for smaller defects in less active patients.
OATS (Osteochondral Autograft Transfer)
This procedure transplants a small plug of healthy cartilage and bone from a non-weight-bearing part of your knee into the damaged area. Because it moves real hyaline cartilage, the results tend to be more durable. In the same 10-year study, 86% of athletes who had this procedure returned to their previous sport level, and only 14% needed revision surgery. It’s best suited for smaller defects since the amount of donor cartilage available from your own knee is limited. For larger defects, donor tissue from a cadaver (allograft) can be used instead.
MACI (Cell-Based Cartilage Implantation)
MACI is the most complex option and the only cell-based cartilage therapy with full FDA approval. It’s a two-stage process. First, a surgeon harvests a small sample of healthy cartilage from a non-weight-bearing area of your knee, roughly the size of a few grains of rice. Those cells are sent to a lab, separated out, and grown on a collagen membrane over three to four weeks. In the second surgery, the surgeon cleans out the damaged area, sizes it with a template, cuts the cell-seeded membrane to fit, and glues it into place. The implanted cells then continue to grow and produce new cartilage matrix within the defect. MACI is particularly useful for larger defects (bigger than 2 cm across) in younger patients.
What About Stem Cell Injections?
Stem cell injections for knee cartilage are widely marketed but far ahead of the evidence. Despite decades of research and hundreds of preclinical studies, MACI remains the only cell-based cartilage product that has achieved FDA approval. No injectable stem cell therapy has cleared that bar. Many clinics offer mesenchymal stem cell injections as an out-of-pocket procedure, but these treatments have not demonstrated consistent cartilage regrowth in rigorous human trials. Some patients report symptom improvement, but whether that reflects actual tissue regeneration or a temporary anti-inflammatory effect remains unclear.
PRP Injections Don’t Regrow Cartilage
Platelet-rich plasma (PRP) injections are another popular option, but the strongest evidence suggests they don’t regenerate cartilage or slow its breakdown. A randomized trial published in JAMA tested PRP against saline placebo injections in 288 adults over 50 with mild to moderate knee osteoarthritis. After 12 months, the PRP group lost 1.4% of their medial tibial cartilage volume while the placebo group lost 1.2%, a difference that was not statistically significant. Pain improvement was also nearly identical between the two groups: 2.1 points on PRP versus 1.8 points on placebo on a 10-point scale. In short, PRP performed no better than saltwater for either pain relief or cartilage preservation.
Do Glucosamine and Chondroitin Help?
Glucosamine and chondroitin are the most popular supplements for joint health, and the evidence is mixed but modestly encouraging for slowing cartilage loss. Several randomized, placebo-controlled trials using MRI to measure cartilage volume found that chondroitin sulfate reduced the rate of cartilage breakdown and slowed joint space narrowing compared to placebo, with effects visible as early as six months. These supplements appear more useful for slowing progression than for rebuilding what’s already lost. They won’t regrow cartilage, but they may help you hold onto more of what you have.
Weight Loss Has an Outsized Impact
If you’re carrying extra weight, losing it is one of the most effective things you can do for your knees. Research on joint biomechanics found that each pound of body weight lost removes roughly four pounds of compressive force from your knee with every step. That ratio adds up fast. Losing just 10 pounds takes about 40 pounds of pressure off your knees per step, which over thousands of daily steps represents a massive reduction in cumulative stress on your remaining cartilage.
Recovery After Cartilage Repair Surgery
Cartilage repair procedures require a longer recovery than many people expect. The new or transplanted tissue needs time to mature and integrate under protected conditions. A typical timeline involves one to three days in the hospital, followed by eight weeks on crutches. Stationary biking usually starts around four to six weeks. Swimming and elliptical training come in at eight to twelve weeks. Light jogging isn’t cleared until about a year after surgery, and unrestricted high-impact activities like basketball or distance running typically require 18 months before they’re safe.
This extended timeline reflects the fundamental biology of cartilage: it matures slowly because it has no blood supply to accelerate healing. Rushing the process risks damaging the repair tissue before it’s strong enough to handle normal loads, which can lead to failure and the need for revision surgery.
Who Is a Good Candidate?
The best candidates for cartilage restoration procedures are younger adults with a single, well-defined area of cartilage damage, healthy surrounding cartilage, and good alignment in the knee joint. If your knee has widespread cartilage loss across multiple areas, which is the pattern in typical age-related osteoarthritis, these procedures are unlikely to help. Older patients and those with multiple lesions are less likely to benefit, and for them, the path often leads toward managing symptoms with weight loss, exercise, and eventually joint replacement if the damage becomes severe enough.
The distinction matters: a 30-year-old with a sports injury that punched a hole in one spot on their cartilage is a very different situation from a 65-year-old whose cartilage has been thinning across the entire joint for decades. The surgical options described above were designed for the first scenario, not the second.